Effect of particle size on the surface properties and morphology of ground flax

Flax fibers were ground with a ball-mill and four fractions with different size ranges were collected by sieving. These were tested for water sorption, degree of polymerization (DP), copper number, hydroxyl number and analyzed by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and inverse gas chromatography (IGC). Significant differences were found between the properties of the flax fiber and those of the ground versions, including fragmentation of fibers, increase of water sorption, copper number, hydroxyl number and surface O/C ratio, and decrease of DP, crystallite size and dispersive component of surface energy (gammasd). Some parameters depended on the particle size: O/C ratio and hydroxyl number had local maxima at 315-630 μm, while gammasd increased steadily with the decrease of particle size. These relationships were explained by fiber disintegration, destruction of waxy surface layer, exposure of cellulosic components, increase of surface area and crystalline imperfections

Characterization of the surface properties of cellulosic fibers in fibrous and ground forms by IGC and contact angle measurements

Surface properties of fibrous and ground cotton and linen were investigated by inverse gas chromatography (IGC) and the contact angle with different liquids was also measured on fabrics composed of both fibers. Results proved that dispersion component of surface tension (γsd) determined by IGC depends not only on the surface energy, but also on several factors influencing the adsorbability of probe molecules on the cellulosic substrates. For cotton samples, the trapping of n-alkanes among waxy molecules in the outer layer of fibers can be presumed. This effect results in larger γsd for cotton fibers than for linen in spite of the higher wettability of the linen fabrics. Besides the surface energy and trapping effects, the grinding also influences the γsd values. Specific enthalpy of adsorption (ΔHAab) of polar probes could be determined on all linen samples, but only on the ground cotton sample. Lewis acid-base character calculated for linen and ground cotton samples depends on the same effects as the γsd does. The similar ΔHAab values of chloroform (acidic) and THF (basic) measured on each of the samples support the conclusion that the surface character is amphoteric, which is also proved by the high ΔHAab values of the amphoteric ethyl acetate and acetone probes

Cellulose nanocrystal/amino-aldehyde biocomposite films

From the suspensions of cellulose nanocrystals (CNCs) derived from cotton and flax by acidic hydrolysis, transparent and smooth films were produced with different plasticizers and an amino-aldehyde based cross-linking agent in a wide composition range by a simultaneous casting and wet cross-linking process. The effect of cross-linker concentration on the optical and tensile properties and on the morphology of CNC films was investigated by various measurements. The interaction of films with liquid water and water vapour was also characterized by water sorption and water contact angle as well as performing a sinking test. Cross-linking improved the transparency, reduced the porosity and surface free energy, and prevented the delamination of CNC films in water at a concentration of 10% or higher. The surface of CNC films is basic in character and has an electron donor property. The CNC/amino-aldehyde films had a high tensile strength (45 MPa) and modulus (11 GPa)

Improving physical properties and retrogradation of thermoplastic starch by incorporating agar

To develop functional and sustainable packaging materials from starch and to enhance their properties, agar was added to thermoplastic corn starch (TPS) in a wide concentration range and the products were prepared either by casting or melt blending with a high glycerol content. The role of agar in the mechanical and barrier performance of films, as well as the compatibility of TPS and agar was systematically evaluated. In addition, the retrogradiation of starch in various blends after long storage periods was widely characterized. Results proved that the addition of agar to TPS resulted in films with promising barrier and tensile properties. Stiffness and strength increased considerably by increasing agar content, while deformability of blends was better than those of pure TPS. Agar incorporation decreased water permeability and solubility and improved light transmittance. Retrogradation of the dry blends was significantly smaller than that of pure TPS owing to the strong starch/agar interaction

Kiváló minőségű cellulóz alapú textíliák előállítása környezetbarát biotechnológiai eljárással = Creation of high-quality cellulose-based textile materials using environmentally friendly biotechnological process

Kutatócsoportunk több mint tíz éve dolgozik a textil biotechnológia területén. Az elmúlt időszakban - a most záruló OTKA pályázat keretén belül - elsősorban a pamut bioelőkészítésére koncentráltunk. Az enzimes előkészítés környezetbarát alternatívája a hagyományos víz-, vegyszer- és energiaigényes lúgos főzésnek, amellyel a nem cellulóz kísérőanyagokat (viaszok, pektin, fehérjék, lignin-tartalmú és színes anyagok) távolítjuk el a szálasanyagból. Kereskedelmi forgalomban kapható hidrolitikus enzimeket - cellulázok, pektinázok, xilanázok - alkalmaztunk pamut és len, valamint ezek keverékeinek bioelőkészítéséhez. Vizsgáltuk az enzimoldathoz adagolt komplexképzők hatását is a kísérőanyagok - elsősorban a viasz és pamutmaghéj - eltávolítására. Jellemeztük a szövetek fehérségét, fehéríthetőségét és színezhetőségét. A kutatás során nyert új eredmények alapján elkezdtük az oxidatív enzimek alkalmazását és hatásuk vizsgálatát a lignin-tartalmú kísérőanyagok bontásában. A drága oxidatív enzimeket szilárdfázisú fermentációval állítottuk elő. Az OTKA által több év óta támogatott kutatómunka tapasztalatai és eredményei jelentették az alapját annak a kutatás-fejlesztési pályázatnak, amelynek keretén belül 2005-ben és 2006-ban pamut, pamut/len és pamut/kender kötött kelmék bioelőkészítésének és biokikészítésének üzemesítése megvalósult. | Our research group has been working with enzymes in textile processes for more than ten years. In the frame of the present research project our primary research interest was in the area of biopreparation with special emphasis on cotton fabric. Enzymatic biopreparation of cellulosics is an environmentally-friendly alternative to the conventional alkaline scouring for removing the non-cellulosic 'impurities' (i.e. waxes, pectins, proteins, lignin-containing impurities and colouring matters, etc.) from greige fibres. Our research thrusts covered the application of commercial hydrolytic enzymes, such as cellulases, pectinases and xylanases for biopreparation of cotton and linen fabrics and their blends; the intensification of bioscouring with chelating agents; the evaluation of the degradation and removal of non-cellulosic matters, especially waxes and cotton seed-coat fragments; the characterization of the dyeing properties of the biopretreated fabrics, as well as the production of oxidative microbial enzymes by solid-state fermentation for efficient degradation of lignin-containing impurities of cotton and linen substrates. Based on the knowledge and experience came from the research supported by the OTKA for many years, implementation of biopreparation and biofinishing technologies in the finishing process of cotton, cotton/linen and cotton/hemp knitted fabrics was realized in 2005 and 2006, respectively, in the frame of a research & development project

The Effect of Surface Characteristics of Clays on the Properties of Starch Nanocomposites

In this research, different clays such as laponite and montmorillonite (NaMMT) are used as fillers in the preparation of thermoplastic starch/clay nanocomposites. Thin films are produced by casting and evaporation in a wide composition range, using glycerol as the plasticizer at two different concentrations. The surface energy of clay fillers is measured by inverse gas chromatography (IGC); X-ray diffraction (XRD) and light transmission measurements (UV-VIS) are carried out to characterize the structure of nanocomposites; and mechanical properties and water vapor permeability are also studied. While all the starch/montmorillonite nanocomposites possess intercalated structures, significant exfoliation can be noted in the starch/laponite nanocomposites, mainly at low clay contents. Due to the larger surface energy of montmorillonite, stronger polymer/clay interactions and better mechanical properties can be assumed in starch/NaMMT composites. The smaller surface energy of laponite, however, can facilitate the delamination of laponite layers. Thus, the specific surface area of laponite can be further increased by exfoliation. Based on the results, the better exfoliation and the much larger specific surface area of laponite lead to higher reinforcement in starch/laponite nanocomposites